1. Field of the Invention
The present invention relates generally to medical devices, and more particularly to an improved catheter for providing radio frequency (RF) treatment to a prescribed region within the spinal canal of a patient. Further in accordance with the present invention, there is provided a method for utilizing such a catheter.
2. Background Art
Radiofrequency (RF) treatment of pain has a long history in the field of pain management, and has been extensively utilized for the treatment of spine pain due to facet joint origin, in particular. Typically, a hollow cannula whose tip is sharp may be inserted percutaneously and positioned under fluoroscopic monitoring over the medial branch nerves that supply the involved facet joints. A probe whose tip emits radiofrequency energy is inserted into the hollow cannula, and causes tissue to heat around the un-insulated cannula tip, resulting in a thermal lesion to the medial branch nerves. With the nerves to the facets joints deactivated, the joints are no longer painful.
Unfortunately, thermal lesions to spinal nerve roots or other painful peripheral nerves often result in a worsening of the pain due to a thermal neuritis. Recently, a non-thermal mode of lesioning using a “pulsed” RF energy has become available with remarkably good results for pain relief. This technique does not produce neuritis, and has allowed for successful RF treatment of painful peripheral nerves. In addition, the technique has been applied to spinal nerve root pain sources, including the Dorsal Root Ganglion (DRG). Pulsed RF lesioning of the DRG has been extensively utilized using a transforaminal approach with generally good results. However, spinal stenosis, post-operative scarring, or other conditions may make the DRG inaccessible via a transforaminal approach; in such a setting, there is no currently available device or technique for performing RF treatment.
Spinal Cord Stimulators are also frequently utilized to target the dorsal root ganglion via the epidural space for treatment of pain stemming from spinal nerve root source. This may be due to conditions such as post herpetic neuralgia, radiculitis from disc disease or foraminal stenosis, post laminectomy syndrome or other neuropathies. The epidural space is accessed through a large bore epidural needle (17 G or 16 G) and then the SCS catheter is inserted into the epidural space and advanced to the target DRG under fluoroscopic guidance. The SCS catheter, once positioned, delivers a current of electrical energy that produces a paresthesia that effectively masks the pain stimulus. If the pain responds to the electrical stimulation, the SCS lead and an electrical generator is permanently implanted within the patient. This procedure with the SCS lead and generator has costs in excess of $20,000, and many patients do not desire a foreign body to be surgically implanted. Furthermore, SCS only serves to disrupt the pain signals by creating a competing parasthesia signal, which can be unpleasant or ineffective for some patients, rather than creating a lesion on the nerves which actually blocks the pain signals from being transmitted. Accordingly, RF lesioning can be more effective for pain management than SCS treatment without having to permanently implant medical devices within a patient.
The pain relief obtained with RF lesioning is similar between the non-thermal pulsed lesioning mode as it is with the standard high temperature lesioning. This suggests that the thermal aspects of the lesion are not the critical elements for obtaining long-term pain relief. The simple application of the radiofrequency electric field appears to be the primary factor. There is emerging substantial body of evidence that the radiofrequency electric field energy when applied to the DRG has neurophysiologic and neurobiological effects at the dorsal horn within the spinal cord. Indeed, the true origin of pain relief from RF treatment may be due to cellular effects on the dorsal horn neurons of the spinal cord, rather than a peripheral thermal lesion of the spinal/peripheral nerve. This evidence suggest that perhaps the dorsal column itself may be a potential target for therapy using RF electric field energy and obtaining sustained pain relief. In this regard, the epidural RF device may also be easily positioned over the dorsal column of the spinal cord, similar to the standard SCS lead placement, and it would be possible to deliver RF energy directly to the dorsal horn. In summary, the epidural radiofrequency catheter is a new device that has current applications for the treatment of spine and nerve pain, and has potential other therapeutic application by way of providing radiofrequency electric field energy to structures within the spinal canal.
Epidural anesthesia is also well known in the medical arts; that is, injecting pain medication through a catheter directly into the epidural space of a patient's spinal canal. However, the analgesic effect of epidural anesthesia is only of a temporary nature. Furthermore, it is impractical and inconvenient to provide repeated epidural injections to a patient for use as a long-term pain management solution.
Accordingly there is a need in the art for a catheter capable of providing RF lesioning treatment directly to critical areas without substantially risking permanently damaging the nerves located in the treatment region. There is also a need in the art for a method of relieving a patient's pain by administering RF energy directly to the patient's spinal nerves. In this regard, a device that can access the DRG via the epidural space, similarly to the SCS lead, and can deliver radiofrequency energy would provide a means of performing radiofrequency treatment to the DRG that is not possible with current technology. This would be an effective, less expensive alternative treatment for spinal nerve pain in patients who are not candidates for, or do not desire, implantable SCS catheter placement.